The present invention relates to several art areas. In one aspect, the invention relates to the recent achievements in building small-scale, micro and nano-size, electromechanical apparatuses and computing components. According to another aspect, the main application of the invention is to facilitate restoring the functionality of an impaired human nervous system. In still other aspect, the invention may modulate the activity of the nervous system.
The evolving area of micro-electromechanical systems (“MEMS”) makes it possible to assemble complex functioning mechanical devices on a level which may not even be recognized by unaided human eye. The dominant portion of new developments in the area of MEMS is geared toward the computer industry, such as development of micro- and nano-scale non-volatile memory, batteries, magnets, capacitors, and motors.
It is generally accepted that the human nervous system consists of the brain, the spinal cord and nerves. A nerve cell is an elementary building block of the nervous system. A nerve cell generally has three identifiable regions: a cell body, or soma, short outgrowths, or dendrites, and a long outgrowth, or an axon. There are a great variety of nerve cells characterized primarily by the difference in the dimension of axon part and the localization of a cell body.
Some nerve cells have all theirs parts located in a single place such as the brain. Other cells have their axons running substantial distances. For instance, the axon may run from the brain along the entire length of a spinal cord. The axon is primarily responsible for conducting signals from one nerve cell to another or for conducting stimulus to and from other organs. Further, the nerve cells whose axons run from and to the brain along the spinal cord interact with other nerve cells, including peripheral nerves, whose cell bodies are primarily located in the so called spinal roots or dorsal ganglia. The nervous system also makes sure that organs and tissues, such as muscles, function properly.
The peripheral nerves are primarily divided into three main groups: (1) sensory, or afferent, (2) motor, or efferent, and (3) nerves of the autonomic system. Further, the nerves in each group are generally subdivided based on the diameter of axon, or a conducting fiber.
An inactive axon usually has a small negative potential, a resting potential, inside the cell due to distribution of ions inside and outside of the axon. An a nerve impulse starts generally when a nerve cell experiences an increased influx of ions, usually sodium ions which leads to depolarization of inner cell membrane of an axon for a short period of time. The depolarization at a particular place in the axon, if it is strong enough, would propagate itself into neighboring regions, generally, by diffusion of sodium ions. Immediately, the increased influx of sodium ions provokes the increased outflow of potassium ions at the place to where the initial impulse came in. In a short period, at the initial place of excitation the system returns to equilibrium, while the depolarization, i.e. the impulse continues to travel along the axon.
Some axons, generally referred to as white matter, stretching for substantial distances, have special shielding material around them which is interrupted by small portions of a naked nerve cell. In such axons, it is believed that the depolarization can only occur at the naked sections allowing the impulse to travel long distances without substantial decrease in its depolarizing ability. Unfortunately, many diseases and injuries may lead to partial or complete severance of the neural conductive pathways, i.e. axons.
For instance, one such injury is a spinal cord injury which could result when a person experiences a catastrophic fall, such as being thrown from a horse or being in a severe car accident. Depending on the area of the spinal cord, the injury may even lead to total paralysis of hands and legs, known as quadriplegic condition. Many thousands of spinal cord injuries occur in the United States each year. It is estimated that it generally costs over four billion dollars to care for people with spinal cord injuries.
There have been many attempts to address the problem of a severed nerve cell. Some attempts concentrate on different ways to secure the severed ends together. Another attempt, in addition to securing both ends of an axon, propose using electro-charged surfaces or surfaces covered with different chemical and biological compositions to stimulate the regeneration. Still other attempts propose uniting the severed ends and using microelectrodes to stimulate the neural endings from an outside source.
While the proposed solutions may provide for a way to hold ends of a severed nerve, they do not overcome a pivotal problem of supporting the propagation of action potential from a primary end to another. Further, many proposed solutions add a substantial outside structure over a severed nerve which may exert negative pressure on the neighboring nerves and other tissue.
U.S. Pat. No. 4,308,868, entitled “Implantable electrical device” discloses a fully implantable and self-contained device composed of a flexible electrode array 10 for surrounding damaged nerves and a signal generator 12 for driving the electrode array with periodic electrical impulses of nanoampere magnitude to induce regeneration of the damaged nerves.
U.S. Pat. No. 5,314,458, entitled “Single channel microstimulator” discloses an implantable microstimulator system employs a miniature ferrite-cored coil contained with an hermetically sealed housing to receive control signals and operating power from an RF telemetry system. The tiny coil receives the electromagnetic energy which is transmitted from a non-implantable transmitter which generates a code-modulated carrier. Demodulator circuitry in the implantable microcircuit is employed to extract the control information, while applying the electromagnetic energy to power the electronic circuitry therein and charge a capacitor which will provide the electrical stimulation to the living being. The electrical stimulation is delivered by a stimulating electrode which has a waffle-like configuration whereby a plurality of iridium oxide electrode pads, coupled in parallel, so as to be characterized by a long effective edge distance, transfer the stimulating charge. The electrical components of the implantable microstimulator are contained within an hermetically sealed housing formed of a glass capsule which is electrostatically bonded to a silicon substrate.
U.S. Pat. No. 5,030,225, entitled “Electrically-charged nerve guidance channels” discloses a medical device is disclosed for use in regenerating a severed nerve. The device includes an implantable, tubular, electrically-charged membrane having openings adapted to receive the ends of the severed nerve and a lumen having a diameter ranging from about 0.5 millimeters to about 2.0 centimeters to permit regeneration of the nerve therethrough. The membrane is fabricated such that an electric charge is exhibited at the inner membrane surface to stimulate regeneration by axonal sprouting and process extension. Also disclosed are methods for repairing a severed nerve and for preparing a medical device for use in regeneration of a severed nerve.
U.S. Pat. No. 4,878,913, entitled “Devices for neural signal transmission” discloses devices and methods for transmitting neural signals from a proximal stump of a transected nerve to a prosthetic apparatus are disclosed employing microelectrodes, preferably conductive fiber networks, capable of sensing electrical signals from a nerve and transmitting such signals to a prosthetic apparatus; and a semipermeable guidance channel disposed about the microelectrodes. The channels include an opening adapted to receive the proximal stump of a transected nerve, such that the channel promotes the growth of the stump and the formation of an electrical connection between the transected nerve and the microelectrode.
U.S. Pat. No. 6,235,041, entitled “Medical device for treatment of a gap or defect in the central nerve system” discloses a medical device (1) of a biocompatible material for use in the treatment of a gap or defect in the central nervous system, which device has a proximal end (5) and a distal end (6) comprising openings (7). The device is adapted to enable connection of nerve fibers of gray and white matter between the proximal end (5) and distal end (6) thereof in predetermined openings (7). The device is of a substantially cylindrical form, or a substantially flat or plate like form and is made of plastic. The openings (7) in at least one end (5, 6) bear distinctively different indicia thereby to indicate whether nerve fibers of gray matter or nerve fibers of white matter are to be inserted therein.
U.S. Pat. No. 5,354,305, entitled “Nerve repair device” discloses a nerve repair device which includes a resilient, elongated implant, and transverse pins for retaining the implant fixedly within the ends of the severed nerve. A sharp tip extends longitudinally from at least one end of the elongated implant, and aids in the insertion of the implant longitudinally through the ends of the severed nerve between the fascicle bundles. The severed ends are retained in close approximation for reconnection.
U.S. Pat. No. 4,778,467, entitled “Prostheses and methods for promoting nerve regeneration and for inhibiting the formation of neuromas” is directed to prosthesis and methods for promoting nerve regeneration. The proximal and distal ends of a severed nerve are brought into close proximity and are enclosed by a tubular prosthesis. In one preferred embodiment, a epineurial or endoneurial monosuture is used to hold the nerve ends in close proximity. A tight seal is formed between the prosthesis and the injured nerve so as to isolate the injured nerve within the prosthesis from the rest of the body of the host. Additionally, in one preferred embodiment, nerve grafts may be incorporated into the prosthesis and nerve regeneration promoting substances may be incorporated within the nerve graft to further enhance nerve regeneration. In another preferred embodiment, a prosthesis is coated with a material which is slippery with relation to the surrounding body tissue and the prosthesis is formed of or coated with a material around the inside of the prosthesis which will substantially adhere to the severed nerve ends so as to prevent substantial movement of the severed nerve ends within the prosthesis. In yet another preferred embodiment, such an outside coating around the prosthesis terminates in two longitudinal flaps which serve to form a fluid-tight seal along the tubular prosthesis. In still another preferred embodiment, the ends of the prosthesis overlap and are formed so as to bias against each other in a spiral tube configuration, thereby providing for firm closure of the prosthesis around a variety of sizes of injured nerves. Also disclosed are various devices and methods for inhibiting the formation of neuromas, such as an open-ended tube or a neuroma-inhibition device formed as a cap member having a reservoir formed therein.
U.S. Pat. No. 4,306,561, entitled “Holding apparatus for repairing severed nerves and method of using the same” discloses circumferentially embracing both the proximal and distal portions of a severed nerve at positions removed from the severed ends and controllably moving the severed portions into abutting, juxtaposed contacting relationship, the reattachment and repair of severed nerves is achieved. Preferably, both portions of the severed nerve are embraced within a holding member which incorporates nerve securing means at the desired location. In addition, the preferred nerve holding member incorporates nerve cooling components, electrical pulse stimulation means for directing a pulse from the proximal portion towards the distal portion, and temperature sensing components for monitoring the temperature of the nerve.
U.S. Pat. No. 5,038,781, entitled “Multi-electrode neurological stimulation apparatus” discloses an implantable system for Functional Electro-Stimulation (FES), which includes an environmentally sealed implant case and a nerve cuff for attaching to the nerve. A plurality of leads connect the nerve cuffs to the case. The implant case provides redundant seals for entrance of the leads in a double wall/double environmental seal to provide long term sealing reliability for the case. Inside the case, the wires in each lead attach to connectors, which establish contact with an enclosed master circuitry case. The connectors allow the leads to be individually removed and replaced, thereby providing a maintainable system. At the other end of the leads is attached the nerve cuff. Each nerve cuff has a hollow, gapped cylindrical shape, and includes electrodes on its inner surface. The cuff is deformable to allow placement around the nerve, holding the electrodes in electrical contact therewith. In other embodiments of the invention, the nerve cuff includes a micro circuit which is capable of demultiplexing stimulation signals from a single pair of wires in the lead to drive multiple electrodes. These embodiments reduce the number of wires needed in each lead to facilitate the stimulation of a large number of nerves with a single implant.
U.S. Pat. No. 5,300,096, entitled “Electromyographic treatment device” discloses an electrical muscle stimulator converts electromyographic (EMG) signals to digital words for analysis and display by a computer program. The therapist selects a variety of different parameters appropriate for the individual patient, and instructs the device to initiate stimulating signals on command, or upon detection of a suitable EMG signal from the patient. The device that converts digital words representing the selected parameters into complex, bipolar therapeutic pulses. The device can digitally model a wide variety of wave forms and graphically assist the therapist in developing and shaping various wave pulse trains.
U.S. Pat. No. 5,041,974, entitled “Multichannel stimulator for tuned stimulation” discloses a multichannel stimulator device having a host user interface circuit for enabling a user to select a channel and easily create and display a stimulus wave signal for the selected channel and generate a data signal specifying the channel and stimulus wave signal. The stimulator also includes a master circuit for receiving the data signal and directing it to the specified channel as a wave building instruction signal. A slave circuit associated with the channel specified receives the wave building signal and responds by generating a corresponding low power stimulus wave signal in the channel specified. Then an output circuit coupled to the slave circuit electrically isolates the low power stimulus wave signal from other channels, amplifying and converting it to a corresponding high fidelity current stimulus wave signal.
U.S. Patent Application No. 20040024439 entitled “Nerve cuff electrode” discloses a nerve electrode system for stimulating and/or monitoring at least one nerve fascicle in a trunk nerve comprising at least one internal electrode and at least one external electrode. The invention also relates to a multi-polar nerve cuff, a method of installing a nerve electrode system or a multi-polar nerve cuff and finally the invention relates to uses of the nerve electrode system or the multi-polar nerve cuff.
U.S. Patent Application No. 20020120309, entitled “System and method for providing recovery from muscle denervation”. Recovery from peripheral nerve and nerve plexus injuries is usually slow and incomplete because the regenerating motor axons often head erroneously toward sensory receptors rather than muscle fibers and because the target muscles atrophy while waiting for the slow process of reinnervation. Research has suggested that electrical stimulation with different waveforms and temporal patterns at different times during the regeneration process might improve the clinical outcome through various mechanisms, but a practical means to deliver such stimulation has been lacking. This invention teaches the use of miniature electrical stimulators that can be implanted alongside the injured nerve(s) at the time of surgical repair and that can be powered and controlled by transmission of radiofrequency energy from outside the body so as to provide a variety of electrical stimuli at different times during the recovery process.
U.S. Patent Application No. 20030176876, entitled “Multi-channel bioresorbable nerve regeneration conduit and process for preparing the same” discloses a multi-channel bioresorbable nerve regeneration conduit and a process for preparing the conduit. The multi-channel bioresorbable nerve regeneration conduit includes a hollow round tube of a porous bioresorbable polymer and a multi-channel filler in the round tube. The multi-channel filler is a porous bioresorbable polymer film with an uneven surface and is single layer, multiple layer, in a folded form, or wound into a spiral shape.
U.S. Patent Application No. 20030153965, entitled “Electrically conducting nanocomposite materials for biomedical applications” discloses exposing osteoblasts on an electrically conducting nanocomposite, which may be an orthopaedic/dental implant, to electrical stimulation enhances osteoblast proliferation thereon. The electrically conducting nanoscale material includes an electrically conducting nanoscale material and a biocompatible polymer and/or a biocompatible ceramic; carbon nanotubes may be used as the electrically conducting nanoscale material.
U.S. Patent Application No. 20010031974, entitled “Neural regeneration conduit” discloses a neural regeneration conduit employing spiral geometry is disclosed. The spiral geometry is produced by rolling a flat sheet into a cylinder. The conduit can contain a multiplicity of functional layers lining the lumen of the conduit, including a confluent layer of adherent Schwann cells. The conduit can produce a neurotrophic agent concentration gradient by virtue of neurotrophic agent-laden microspheres arranged in a nonuniform pattern and embedded in a polymer hydrogen layer lining the lumen of the conduit.
U.S. Patent Application No. 20020193858 entitled “Miniature implantable connectors” discloses methods of making electrical connections in living tissue between an electrically conductive wire and an implantable miniature device. The device may either stimulate muscles or nerves in the body or detect signals and transmit these signals outside the body or transmit the signals for use at another location within the body. The device is comprised of an electrically insulating or electrically conductive case with at least one electrode for transmitting electrical signals. The electrodes and the wire-electrode connections are protected from the aggressive environment within the body to avoid corrosion of the electrode and to avoid damage to the living tissue surrounding the device.
U.S. Patent Application No. 20040015205 entitled “Implantable microstimulators with programmable multielectrode configuration and uses thereof” discloses miniature implantable stimulators (i.e., microstimulators) with programmably configurable electrodes allow, among other things, steering of the electric fields created. In addition, the microstimulators are capable of producing unidirectionally propagating action potentials (UPAPs).
U.S. Patent Application No. 20040015204 entitled “Implantable microstimulators and methods for unidirectional propagation of action potentials” discloses miniature implantable stimulators (i.e., microstimulators) are capable of producing unidirectionally propagating action potentials (UPAPs). The methods and configurations described may, for instance, arrest action potentials traveling in one direction, arrest action potentials of small diameters nerve fibers, arrest action potentials of large diameter nerve fibers. These methods and systems may limit side effects of bidirectional and/or less targeted stimulation.
U.S. Patent Application No. 20030181956 entitled “Multi-purpose FES system” discloses a multi-purpose FES system which includes a multi-function, implantable stimulator for stimulating different sites in a patient's body. The stimulator includes a control unit and a receiving device. The stimulator further has a plurality of bundles of electric leads connected to the control unit, each lead terminating in at least one electrode to provide a plurality of discrete groups of electrodes associated with each site. Each group of electrodes is operable to stimulate its associated site in the patient's body, under the action of stimulation signals from the control unit, the control unit receiving signals from the receiving device. A transmitter is arranged externally of the patient's body for supplying signals transcutaneously to the receiving device of the stimulator. A controller is in communication with the transmitter via a communications interface unit.
U.S. Patent Application No. 20030171785 entitled “Distributed functional electrical stimulation system” discloses a multi-purpose, functional electrical stimulation (FES) system includes an implantable stimulator unit for stimulating a plurality of different sites in a patient's body. A transmitter is arranged externally of the patient's body for supplying signals transcutaneously to the stimulator unit. A controller is in communication with the transmitter. At least one implantable switching node has an input terminal in electrical communication with the stimulator unit and a plurality of output terminals to each of which one of a further switching node and a stimulating element is connected. The switching node including addressing circuitry for switching at least one output terminal into electrical connection with the input terminal of the switching node in response to a control signal received from the controller via the stimulator unit.
U.S. Patent Application No. 20030149457 entitled “Responsive electrical stimulation for movement disorders” discloses an implantable neurostimulator system for treating movement disorders includes a sensor, a detection subsystem capable of identifying episodes of a movement disorder by analyzing a signal received from the sensor, and a therapy subsystem capable of applying therapeutic electrical stimulation to treat the movement disorder. The system treats movement disorders by detecting physiological conditions characteristic of an episode of symptoms of the movement disorder and selectively initiating therapy when such conditions are detected.
U.S. Patent Application No. 20030144710 entitled “Method and implantable systems for neural sensing and nerve stimulation” discloses an invention which relates to methods and apparatuses for the detection of neural or muscular activity, analysis of the signals and the subsequent stimulating of neural or muscular tissue based thereon. According to a first aspect of the invention an apparatus for producing a muscular action is provided, comprising a combined sensing and stimulation electrode device comprising at least one neurosense electrode means capable of sensing a nerve signal from a peripheral nerve and at least one stimulation electrode means capable of stimulating a peripheral motor nerve fibre, means for receiving and processing the sensed neurosignals to identify a signal indicative of a specific action, especially a component of the gait performed by the patient and for producing a control signal in response thereto, and means for operating the at least one stimulation electrode means in response to the control signal to produce a stimulation of a peripheral motor nerve fibre.
U.S. Patent Application No. 20010000187 entitled, “Functional neuromuscular stimulation system” discloses an input command controller (A) provides logic function selection signals and proportional signals. The signals are generated by movement of a ball member (12) and socket member (14) relative to two orthogonal axes. When the joystick is implanted, a transmitter (50) transmits the signals to a patient carried unit (B). The patient carried unit includes an amplitude modulation algorithm such as a look-up table (124), a pulse width modulation algorithm (132), and an interpulse interval modulation algorithm (128). The algorithms derive corresponding stimulus pulse train parameters from the proportional signal which parameters are transmitted to an implanted unit (D). The implanted unit has a power supply (302) that is powered by the carrier frequency of the transmitted signal and stimulation pulse train parameter decoders (314, 316, 318). An output unit (320) assembles pulse trains with the decoded parameters for application to implanted electrodes (E). A laboratory system (C) is periodically connected with the patient carried unit to measure for changes in patient performance and response and reprogram the algorithm accordingly. The laboratory system also performs initial examination, set up, and other functions.
U.S. Patent Application No. 20030208246 entitled “Electrostimulation system with electromyographic and visual biofeedback” provided an electrostimulation system with electromyographic and visual biofeedback for sensing electromyographic impulses and facilitating muscular activity. The electrostimulation system comprises stimulator that is adapted to generate an electric impulse and at least one pair of electrodes adapted to transmit the electric impulse or to receive electromyographic impulses. The system further comprises an amplifier electrically communicating with the pair of electrodes, the amplifier is adapted to amplify the received electromyographic impulses and a filtering unit electrically communicating with the amplifier and is adapted to remove artifacts from the received electromyographic impulse. A commutation block is electrically communicating with the pair of electrodes and is adapted to alternately transfer the electromyographic impulses to the amplifier or to transfer the generated electric impulse from the stimulator. A display for displaying the received electromyographic impulses and a predetermined threshold value is also provided as well as a control unit that is adapted to receive the electromyographic impulses from the amplifier and to activate the stimulator in a predetermined manner. The stimulator incorporated in the present invention is triggered to transmit impulses to the rehabilitated muscle when the electromyographic impulse substantially equals or exceeds the predetermined threshold value.
One type of prior art solution attempts to deal directly with the aftermath of a spinal cord injury by trying to somehow repair the severed nerve cells. Another type of prior art solution concentrates on addressing the consequences of a spinal cord injury such as the inability of an injured person to control bodily functions below the injured area. Such solutions propose external micro-stimulators which are placed around or embedded into one or several peripheral nerves and which stimulate those nerves in accordance with a necessary regime.
Most solutions consist of a conducting plate or a plurality of micro-electrodes. Some solutions propose a system in which micro-stimulating an implant may have power generating and storing ability, an ability to communicate, and an ability to affect the propagation of action potential in a nerve.
However, implant systems have certain disadvantages. One disadvantage is an implant imposes a substantial outside structure over a nerve. The nerve may exert negative pressure on the neighboring nerves and other tissue. Another disadvantage is that such implant is unable to fully function autonomously because of its inability to convert the electrochemical energy of an action potential into an electrical power. Still other disadvantage is that such a system lacks the functionality to read the nerve cell own action potentials and to produce or modulate the action potentials based on these readings without reserving to any external communications.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and claims.